This invention relates to a safety valve for the second stage regulator of a self-contained underwater breathing apparatus or scuba equipment and, more particularly, to a manually operated safety valve for controlling the air supply to the second stage regulator.
A self-contained underwater breathing apparatus or "scuba" equipment typically includes a pressurized air cylinder with a first stage regulator and dispensing elements with one or more second stage regulators coupled thereto, to provide breathable air to a diver at a controlled rate and pressure. On the water surface as well as while diving, malfunction of second stage regulators has presented a number of problems. More particularly, the second stage regulator is combined with a mouthpiece for dispensing air to the diver and is operated by the pressure differential generated by the diver's breathing. Negative pressure generated during inhalation acts on a diaphragm which actuates a needle valve allowing pressurized air to ventilate the diver's lungs. Positive pressure generated during exhalation on the other hand acts on the diaphragm to close the needle valve and enables venting of the exhaled gasses to the exterior, for example, into the water where it forms the bubbles typically associated with scuba diving.
If foreign matter is introduced into the needle valve of the second stage regulator, the valve may stick in the open or partially open position thus venting valuable supply air through the regulator to the exterior. This prevents proper operation of the device and decreases the life of the air cylinder, possibly jeopardizing the diver. Indeed, this poses a significant hazard during diving as the supply air may be vented to the exhaust before the diver can safely surface. The installation of a back-up second stage regulator on an additional hose in the event the first second stage regulator fails does not overcome this problem because the faulty second stage regulator will continue to vent supply air unless supply air to that regulator can be quickly and easily interrupted by the diver.
Another problem associated with second stage regulators arises when a surface check out of scuba equipment reveals a free-flowing second stage regulator which vents supply air to the atmosphere before the dive. This may cause exhaustion of the air cylinder sufficient to warrant postponement or cancellation of the dive unless additional pressurized cylinders are available at the site.
It would therefore be desirable to provide a means for manually cutting off the supply of air to the second regulator valve prior to a dive as well as during the dive so that undesirable venting of supply air either before or during the dive is prevented.